In microscopic observation, a microscope objective lens with as long working distance as possible is desired to facilitate handling of a sample. However, a focal length of a lens group arranged on an object side needs to be long to secure a long working distance. Furthermore, when the focal length of the lens group is taken into account, a space for the arrangement of the lenses is limited, and correction of aberrations, particularly high-order spherical aberration and chromatic aberration, becomes difficult. Therefore, a lens system using a diffractive optical element (DOE) is proposed (for example, see Patent Literature 1). The use of the diffractive optical element allows advanced correction of the chromatic aberration, and necessary correction by the lenses is therefore the correction of the spherical aberration.